1. Field of the Invention
The present invention relates to an apparatus for measuring light characteristics on a video screen and for the calibration of video output devices such as video monitors, video projectors and the like.
2. Description of Related Art
When calibrating displays such as flat screen televisions, video projector and screen systems and video monitors there are several color analyzers on the market which can accurately measure the light being emitted by the display. The analysis includes measuring light output of a display at different frequencies or different colors. Although each may measure the light emitted by the display accurately, light added to the display from other sources will be included in the analysis results. The difficulty lies in the situation where the analysis must be performed in different ambient light settings than that of during viewing of the display. An example of this would be where a calibration of a screen is performed in daylight conditions where the screen viewing will primarily be during darker conditions.
Pod style analyzers which lie flat against the screen may aid in this situation, but is usually limited to rear projection and self emitting displays such as LCD, CRT, LCOS, DLP, and Plasma. Front projector calibration cannot be performed accurately since the pod itself will block the light from reaching the screen at the position where the light sample is generally taken. Even when used on the self emitting displays, light can easily leak in between the screen and the actual sensor since most of the pods have the sensor set back a small distance from the screen by a series of suction cups.
In measuring video displays, devices which are aimed at the screen from a distance rather than being placed directly against the screen generally provide more accurate measurements. However, devices which lie against the screen may be used instead of the aiming device for the sole purpose of reducing ambient light. These devices cannot be used in front projection systems and are questionable in their ability to screen all ambient light. It would be convenient to have an analyzer system to aid in calibration of video displays during high ambient light conditions yet be able to calibrate the display properly for low or no ambient light viewing.
The problem of ambient light affecting desired readings in an optical sensor may pertain to color analyzers, spectrophotometers, tri-stimulus sensors as well as any type of optical sensor or light wave sensors. One example of an optical sensor is the OTC1000 manufactured by Sencore in South Dakota. The drawings and test data in this application use the OTC1000 as the color analyzer as a reference although the present invention may be used in combination with many light wave sensors or light wave analyzers on the market. The color analyzer, light wave analyzer, optical comparator and light analyzing are examples of devices used to analyze light projecting from a video display screen and are all devices used in combination with the ambient light block apparatus.